2 6-bis(3 5-dialkyl-4-hydroxybenzyl) cycloalkanones

ABSTRACT

DISCLOSED ARE NOVEL 2,6-BIS(3,5-DIALKYL-4-HYDROXYBENZYL)CYCLOALKANONES WHICH ARE USEFUL ANTIOXIDANTS FOR OLEFIN POLYMERS. THE PARTICULAR 2,6-BIS(3,5-DIALKYL-4-HYDROXYBENZYL)CYCLOALKANONES OF THIS INVENTION HAVE THE FORMULA   (CH2)N&lt;(-CH(-CH2-(3,5-DI(R-)-1,4-PHENYLENE)-OH)-CO-CH(-CH2   -(3,5-DI(R-)-1,4-PHENYLENE)-OH)-)   WHEREIN R IS A HYDROCARBON RADICAL AND N IS AN INTEGER OF 2 OR 3. THESE COMPOUNDS ARE USEFUL AS PROTECTIVE AGENTS FOR POLY(ETHYLENE), POLY(4-METHYLPENTENE-1), POLY(PROPYLENE) AND OTHER OLEFIN POLYMERS.

United States Patent O 3,631,148 2,6-BIS(3,5-DIALKYL-4-HYDROXYBENZYL)CYCLOALKANONES Robert A. Krueger, Cuyahoga Falls, Ohio, assignor to TheB. F. Goodrich Company, New York, N.Y.

No Drawing. Original application Nov. 1, 1967, Ser. No.

679,622. Divided and this application Apr. 9, 1970, Ser.

Int. Cl. C08f 45/58 US. Cl. 26045.85 6 Claims ABSTRACT OF THE DISCLOSUREDisclosed are novel 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanoneswhich are useful antioxidants for olefin polymers. The particular2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones of this inventionhave the formula of 2 or 3. These compounds are useful as protectiveagents for poly(ethylene), poly(4-methy1pentene-1), poly(propylene) andother olefin polymers.

This is a division of application Ser. No. 679,622 filed Nov. 1, 1967.

BACKGROUND OF THE INVENTION Hindered phenols are recognized as usefulprotective agents against the deleterious affects of oxygen for a widevariety of materials including polymeric materials, oils, fats, etc. Ofmuch recent interest are antioxidants of the hindered phenol typewherein the hindered phenol is attached to an ester function, especiallywhere the carbonyl of the ester moiety is separated from the aromaticring of the phenol moiety by two carbon atoms, that is, the carbonyl isin the beta position. Many feel that the enhanced reactivity of thesecompounds towards oxygen is due to the carbonyl group in the betaposition.

Although molecular weight by itself is not the sole consideration in thechoice of an antioxidant it is nevertheless an important factor. Ingeneral, higher molecular weight materials are less volatile andtherefore better suited for use with polymeric materials which often areprocessed at elevated temperatures, however, for most efiicientprotection the weight ratio of hindered phenol to overall molecularweight of the compound should also be high.

SUMMARY OF THE INVENTION I have noW prepared2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones which are usefulantioxidants for olefin polymers. The2,6-bis(3,5-dialkyl-4-hydroxybenzyl) cycloalkanones are unusual in thatthey contain a single carbonyl group which is beta to two hinderedphenol groups. These compounds provide high molecular weight materialshaving a high weight ratio of hindered phenol to overall molecularWeight. The 2,6-bis(3,5-dialkyl-4- hydroxybenzyl(cycloalkanones of, thepresent invention are particularly effective antioxidants for olefinpolymers such as poly(ethylene), poly(propylene), poly(butene-l),poly(isobutylene), poly(4-methylpentene-1) and ethylene-propylenepolymers.

DETAILED DESCRIPTION OF THE INVENTION The novel2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones of this inventionhave the structural formula wherein R R R and R are alkyl, cycloalkyl oraryl groups either the same or different having from 1 to 8 carbon atomsand n is 2 or 3. Especially preferred antioxidants of the presentinvention are compounds wherein R R R and R are tertiary alkyl groupscontaining from 4 to 8 carbon atoms. Such tertiary alkyl groups willinclude tertiary-butyl, 1,1,3-trimethylpropyl, 1,1,2-trimethylpropyl,l-methyl-l-ethylpropyl, 1,1-diethylpropyl, 1,1,2,2-tetramethylpropyl,1,1,3-trimethylbutyl, 1,1,2-trimethylbutyl, 1,1-dimethylpentyl and thelike. Especially effective antioxidants will contain two tertiary butylgroups adjacent to the hydroxyl group on the aromatic nucleus, such as2,6-bis(3,5-di-tertiary-butyl-4-hydroxybenzyl)cyclohexanone and2,6-bis(3,5-di-tertiary-butyl-4hydroxybenzyl cyclopentanone.

The 2,6-bis(3,5-dia1kyl 4 hydroxybenzyDcycloalkanones are high meltingcrystalline solids, generally having melting points above about 200 C.,which are soluble in a Wide variety of solvents. Suitable solventsinclude: organic hydrocarbons such as benzene, toluene, hexane, heptaneand the like; chlorinated hydrocarbons such as chlorobenzene and carbontetrachloride; alcohols such as methanol, ethanol and isopropanol;ketones such as acetone and methylethyl ketone and the like.

Preparation of the 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones ofthe present invention is conveniently carried out by reacting an enamineof cyclopentanone or cyclohexanone with a molar excess of a3,5-dialkyl-4- hydroxybenzyl halide. The reaction is normally conductedat atmospheric pressure in a solvent such as methanol, dioxane, toluene,benzene or the like at a temperature ranging between about 50 C. and C.Following the reaction the reaction product is hydrolyzed by treatingwith water for about 15 to 30 minutes to obtain the 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanone;

The compounds of this invention are useful as protective agents for awide variety of polymeric materials sus ceptible to oxidativedegradation. In general, polymeric materials derived from thepolymerization of olefin monomers containing a vinylidene (CH =Cgrouping and containing from 2 to 9 carbon atoms are found to beeffectively protected. Polymerizable monomers of the above type include:olefins such as ethylene, propylene, butene-l, pentene-l, hexene-l,octene-l, isobutylene, 4- methylpentene-l, methylbutene-l,2methylhexene-1, and 2-ethylhexene-l; diand polyolefins such as1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4,7-octatriene,butadiene and isoprene; mixture and the like. The abovementionedmonomers may be homopolymerized or mixtures of one or more of thesemonomers may be copolymerized to form the polymerizates useful for thepresent invention.

Small amounts of the 2,6-bis(3,5-dialkyl-4-hydroxybenzyl(cycloalkanonesare particularly efiective antioxidants for poly(ethylene),poly(propylene), poly(butene-l), poly(isobutylene),poly(4-rnethylpentenel), ethylene-propylene copolymers andethylene-propylene terpolymers wherein the third monomer is1,4-hexadiene, 2-methyl-l,4-hexadiene, the dimethyl-1,4,9-decatrienes,diacyclopentadiene, vinyl cyclohexene, vinyl norbornene, ethylidenenorbornene, methylene norbornene. norbornadiene, methyl norbornadiene,methyl tetrahydroindene or the like. They also find use in otherpolymers such as polystyrene, isobutylene-styrene copolymers,isobutylene-isoprene copolymers, polybutadiene, butadiene-styrenecopolymers, butadiene-acrylonitrile copolymers, butadienevinyl pyridinecopolymers, butadienc-acrylic acid copolymers, butadiene-alkyl acrylateor methacrylate copolymers, butadiene-chlorostyrene copolymcrs,butadienemethyl vinyl ketone copolymers. polyisoprene, polychloropreneand the like, and other materials. The 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones may also be used as protectiveagents for other materials such as pitroleum products, vegetable oils,animal fats and the The antioxidants of the present invention arereadily incorporated into the olefin polymers by conventional techniquesand generally require no special processing. They are mixed into theolefin polymers as solids on a mill or with an internal mixer orkneader; in solutions or dispersions of the olefin polymers; or insolvents masterbatched with other compounding ingredients. They may beused in the olefin polymers in combination with other conventionalcompounding ingredients such as processing oils, plasticizers,lubricants, anti-sticking agents, fillers. pigments, reinforcing agents,sulfur and other curing agents, accelerators, stabilizers, antioxidants,antiozonants, and the like.

In combination with other antioxidants, the 2.6-bis(3.5-dialkyl-4-hydroxybenzyl)cycloalkanones often show synergistic activity.Other antioxidants which may be used in combination with the compoundsof this invention include amines and their derivatives and phenols andtheir derivatives, such as:

2,6-ditertiary-p-cresol;

2,2'-methy1enebis( 6-tertiary-butyl-p-cresol); 2,2-methylenebis[6-(2-rnethylcyclohexyl p--cresol]; 4,4'-butylidenebis(6-tertiary-butyl-m-cresol); 4,4-ethylidenedi-o-cresol;4,4'-thiobis(6-tertiary-butyl-m-cresol); 1,5-naphthalenediol;

1,1-thiodi-2-naphthol;

N-phenyl-l-naphthylamine; N-phenyl-Z-naphthylamine;N,N'-di-2-naphthyl-p-phenylenediamine:l.l'-thi0bis(N-phenyl-2-naphthylamme l: N,N'- (iminodiethylene)bisoctadecanamide:

salts or amides of 3,3'-thiodipropionate; dilaurylthiodipropionate;l,2-dihydro-2.2,4-trimethyl-6-phenylquinoiine2 Z-benzimidazolethiol;

5,5-dimethylacridan;

and the like.

The amount of the 2,6-bis(3.5-dialkyl-4-hydroxybenzyl) cycloalkanonesemployed will vary with the particular olefin polymer to be protected.Generally. however. the 2,6-bis(3,5dialkyl-4-hydroxybenzyl)cycloalkanones will range between about 0.01% byweight and about 10% by weight based on the polymer and more preferablybetween about 0.05% and 4% by weight. If used in combination withanother antioxidant, the combined antioxidant level will not exceed 10%by weight based on the polymer and preferably will be from 0.1 to

The following examples illustrate the invention more fully, however,they are not intended to limit the scope thereof. All parts andpercentages are reported on a weight basis unless indicated otherwise.

4 Example I 2,6-bis(3.5 di tertiary-butyl-4-hydroxybenzyl)cyclohexanonewas prepared by first dissolving 15 grams (0.1 mol) ofl-(N-pyrolydyl)cyclohexene and 25.5 grams (0.1 mol) of3,S-di-tertiary-butyl-4-hydroxybenzyl chloride in about mls. of dioxaneand then heating the reaction mixture at reflux for about 2.5 hours.About 15 mls. of water was added and the mixture stirred an additional15 minutes. Fractional distillation of the reaction mixture at reducedpressure (0.08 mm. Hg) yielded several viscous fractions collectedbetween 147 C. and 183 C. which when combined and recrystallized fromisopropyl alcohol gave a light powder, melting point 8788 C. Analyticaldata indicated this product was the mono-substituted de rivative, 2-(3,5-di-tertiary butyl-4-hydroxybenzyl)cyclohexanone. The pot residueremaining after fractionation was twice recrystallized from isopropylalcohol. The resulting white crystalline product had a melting point of22l-Z23 C. and nuclear magnetic resonance analysis confirmed thecompound was 2,6-bis(3,5-di-tertiary-butyl-4-hydroxybenzyl)cyclohexanone.

Example II 2,6-bis(3,5 di tertiary-butyl-4-hydroxybenzyl)cyclohexanonewas incorporated into a poly(4-rnethylpentenel) polymer to demonstrateits use as an antioxidant. The particular poly(4-methylpentene-l)polymer employed was an olefin copolymer containing about to 97% 4-methylpentene-l interpolymerized and having a density of 0.83. The2.6-bis(3,5-di-tertiary butyl-4-hydroxybenzyl)cyclohexanone wasdissolved in 100 mls. acetone and 10 grams of thepoly(4-methylpentene-1) copolymer added. The mixture was then strippedto dryness in a rotary evaporator and the resulting powder pressed into5" x 5" squares having a thickness of 11-14 mils. The pressing operationwas conducted at 270 C. and 20,000 p.s.i. for 10 minutes after 5 minutesof preheating at moderate pressure.

A modified Scott Tester Block was used to measure the oxygen absorption.One inch circles were cut from the 0.012" sheets and pressed ontoaluminum screen with heat and pressure. Six samples were placed in eachtesting tube and the system thoroughly flushed and filled with oxygen.The tubes were maintained at 140 C. and the induction periodsdetermining by noting the oxygen absorption at regular intervals.Results of the oxygen absorption tests are set forth in Table I below.Results reported in Table I include a control polymer which contains noantioxidant as well as polymers containing the2,6-bis(3.5-di-tertiary-butyl 4 hydroxybenzyl)cyclohexanone alone and incombination with dilaurylthiodipropionate.

TABLE I Samples were also subjected to C. temperatures in anair-circulating oven for prolonged periods. At regular intervals thesamples were removed from the oven and analyzed by infra-red todetermine if a significant increase in carbonyl content had occurred,and if so, the samples were deemed to have failed, Table 11 reports theresults of one such oven-aging test.

TABLE II Hours to failure Control (no antioxidant) 242,6-bis(3,5-di-tertiary-butyl-4-hydroxybenzyl) cyclohexanone (0.1 phr.)670 2,6-bis(3,5-di-tertiary-butyl-4-hydroxybenzyl) cyclohexanone (0.1phr.)+dilaurylthiodipropionate (0.2 phr.) 840 When the2,6-bis(3,S-di-tertiary-butyl-4-hydroxybenzyl) cyclopentanone wasemployed, similar results were obtained-the compounds proving to beefiective antioxidants for poly(4-methylpentene-l) subjected to the 140C. oxygen absorption test or the 125 C. air-circulating oven test.

The 2,6-bis(3,5-di-tertiary butyl-4-hydroxybenzyl)cyclohexanone is overthree times more effective as a protective agent than the2-(3,5-di-tertiary-butyl-4-hydroxybenzyl cyclohexanone.

Example III The antioxidants of this invention were tested inhighdensity polyethylene. The 2,6-bis(3,5-di-tertiary-butyl-4-hydroxybenzyl)cyclohexanone and several commercial antioxidants wereseparately weighed, dissolved in acetone and then added to theunstabilized high-density polyethylene (density=0.9'6) suspended inacetone. The mixture was stripped to dryness in a flash evaporator andmilled for about 5 minutes at 290-300 F. The polymer was thencompression molded into 0.010" thick sheets. Samples cut from thesesheets were then tested for oxygen absorption in accordance with theprocedure described in Example II. Oxygen absorption data is set forthin Table III.

TABLE III Induction period (hours) Control (no antioxidant) 32,6-bis(3,5-di-tertiary butyl 4 hydroxybenZyDcyclohexanone (0.1 phr.)Octadecyl 2 (3,S-di-tertiary-butyl-4-hydroxyphenyl) propionate (0.1phr.) 1 77 Pentaerythrityl tetrakis2-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate (0.1 phr.) 1 78l,1,3-tris(S-tertiary-butyl 2 methyl-4-hydroxyphen- 78 copolymer asmight be used for tire treads and an ethylene, propylene, 1,4-hexadieneterpolymer.

The examples clearly demonstrate the efiectiveness of the novel2,6-bis(3,5-dialkyl-4-hydroxybenzyl) cycloalkanones of the presentinvention as antioxidants for olefin polymers. It is evident from TablesI, II and III that the oxidative stability of high-density polyethyleneand poly (4methylpentene-1) which has been subjected to an oxygenatmosphere at 140 C. or air at C. is markedly improved. In the oxygenabsorption test, the 2,6-bis(3,5- di-tertiary-butyl 4hydroxybenzyl)cyclohexanone performs better than antioxidants havingsimilar structures which are Widely used throughout the industry. Whencombined with dilaurylthiodipropionate, the 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanones give a synergistic effect.

I claim:

1. A composition comprising a synthetic olefin polymer and about 0.01%to 10% based on the weight of the polymer of a2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanone having the formula R10 R3 H 1 n 1 R3 R4 wherein R R R and R are tertiary alkyl groupscontaining from 4 to 8 carbon atoms and n is 2 or 3.

2. The composition of claim 1, wherein the 2,6-bis (3,5-dialkyl-4-hydroxybenzyl)cycloalkanone is2,6-bis(3,S-ditertiary-butyl-4-hydroxybenzyl)cyclohexanone.

3. The composition of claim 1, wherein the 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanone is2,6-bis(3,5-ditertiary-butyl-4-hydroxybenzyl) cyclopentanone.

4. The composition of claim 1, wherein the olefin polymer ispoly(ethylene).

5. The composition of claim 1, wherein the olefin polymer ispoly(4-methylpentene-l).

6. The composition of claim 1, which contains dilaurylthiodipropionateand a 2,6-bis(3,5-dialkyl-4-hydroxybenzyl)cycloalkanone in an amount notexceeding 10% based on the weight of the polymer.

References Cited UNITED STATES PATENTS 2,803,660 8/ 1957' Garber 260-5902,883,365 4/ 1959 Mathes 260-4595 2,914,463 11/ 1959 Beaver et al.252-404 2,894,004 7/ 1959 Dietzler 260-4595 DONALD E. CZAJA, PrimaryExaminer V. P. I-IOKE, Assistant Examiner US. Cl. X.R.

